The Applicant has previously described a method of enabling users to access information from a computer system via a printed substrate e.g. paper. The substrate has coded data printed thereon, which is read by an optical sensing device when the user interacts with the substrate using the sensing device. A computer receives interaction data from the sensing device and uses this data to determine what action is being requested by the user. For example, a user may make handwritten input onto a form or make a selection gesture around a printed item. This input is interpreted by the computer system with reference to a page description corresponding to the printed substrate.
It would be desirable to improve to enable the sensing device to read standard linear barcodes without special modifications or selection of a special barcode-reading mode by the user.